Error: "The report schedule <ReportName> has failed" (4237333)

When running a Report schedule, the report file gets created correctly however the email has the following error:

"The report schedule has failed. To view the reason for the failure, go the Schedule Explorer in the Report Manager, or contact your Reporter administrator. I have verified that there are no illegal characters in the name"

This behaviour usually occurs if the size of the report file exceeds 1MB or if the report exceeds the SMTP server attachment limit. 

Please see this KB article for instructions on how to increase the maximum attachment size in Enterprise Reporter.